The present invention generally relates to electrochemical cells and, more particularly, to a non-cylindrical electrochemical cell configured to prevent excessive deformation of the cell container.
Electrochemical cells are commonly employed to supply voltage for electrically operated devices, and are particularly well-suited for use with portable electrically operated devices. Currently, the popular conventional alkaline cells are of a generally cylindrical shape which are commercially available in industry standard sizes including D-, C-, AA-, AAA-, and AAAA-size cells, as well as other sizes and configurations. Electrochemical cells, such as the aforementioned cylindrical type, commonly provide for a predetermined open circuit voltage supply.
Conventional cylindrical alkaline cells generally employ a cylindrically-shaped steel can provided with a positive cover at one end and a negative cover at the opposite end. The cylindrical cell has a positive electrode, commonly referred to as the cathode, which is often formed of a mixture of manganese dioxide, potassium hydroxide solution, water, and other additives, formed about the interior side surface of the cylindrical steel can. A cup-shaped separator is generally centrally disposed in an inner cylindrical volume of the can about the interior surface of the cathode. A negative electrode, commonly referred to as the anode, is typically formed of zinc powder, a gelling agent, and other additives, and is disposed along with the electrolyte solution within the separator.
While cylindrical cells of the aforementioned cylindrical kind have become quite popular, it has been discovered that there is potential need to provide for non-cylindrical cell configurations. One such need exists for use in a multiple-cell battery, such as 9-volt battery, which commonly houses six 1.5-volt cells electrically connected in series. In the past, multiple cylindrical cells have been assembled together in a rectangular container, thereby resulting in unused space between adjacent cells as well as between each cell and the inside walls of the rectangular battery container. In addition, it has been discovered that many battery operated devices are capable of using non-cylindrical cells, which may offer increased service performance. Examples of non-cylindrical cells are disclosed in U.S. Pat. No. 6,168,883 issued on Jan. 2, 2001, and U.S. Pat. No. 6,081,992, issued on Jul. 4, 2000, both of which are hereby incorporated by reference.
The cells disclosed in the aforementioned co-pending applications are prismatic with a substantially rectangularly configured steel can containing the active cell materials. The rectangular steel can includes four substantially planar side walls. As an electrochemical cell discharges, pressure can buildup inside the cell. Excessive pressure buildup can potentially lead to bulging of the side walls of the can which in turn may cause some difficulties in removing the battery from a device. Excessive bulging may also force the inner walls of the can away from and out of contact with the cathode, and may thereby reduce performance of the cell. Accordingly, it is a goal in designing alkaline cells to increase the service performance of the cell, while at the same time preventing excessive bulging of the cell.
The present invention reduces can deformation, such as bulging, of a non-cylindrical electrochemical cell, by providing the can with inwardly curved side walls to oppose radially outward forces such as that caused by internal pressure buildup within the cell. To achieve this and other advantages, and in accordance with the purpose of the invention as embodied and described herein, the present invention provides for an electrochemical cell having a container having a top end, a bottom end, and one or more side walls, in which at least one of the side walls has at least one inwardly curved groove formed around a perimeter of the container and extending radially inward. The electrochemical cell further includes first and second electrodes and a separator disposed therebetween. A cover and seal assembly is assembled to the top end of the container. The first electrode is formed against the interior surface of the container including a surface of the at least one inwardly curved groove. The inwardly curved groove of the side walls provides enhanced opposition to forces caused by internal pressure within the cell so as to reduce and/or prevent bulging of the cell walls.
These and other features, objects, and benefits of the invention will be recognized by those who practice the invention and by those skilled in the art, from reading the following specification and claims, together with reference to the accompanying drawings.